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2 _Parasaurolophus_ honking...



Stang1996@aol.com (Peter Buchholz) responds to Rob Meyerson:

> You're missing the point now.  The TRUMPET is NOT what makes the
> sound; the player's LIPS and the MOUTHPIECE make the sound, the
> trumpet simply amplifies and difines the range of the sound.

This time I'm afraid I'm going to have to disagree (although I suppose
you could hedge a bit in terms of the definition of "make the sound").
If what you were saying were correct, then changing the position of
the slide on a trombone, opening and closing the valves on a trumpet
or adding a mute to a instrument's bell would not have the effects
that they do.  The body of the trumpet is responsible for the pitches
and timbres of each of it's possible "notes".  The mouthpiece (and
attached mouth) only initiates the vibrations (i.e. picks which of the
trumpet's notes will be played).  While the mouth and mouthpiece are
important, they are certainly not the whole story.  Have you ever
played a trumpet's mouthpiece into a microphone instead of a trumpet?

Let me also take this opportunity to modify something that I
previously wrote.  In describing acoustic waveguides, I claimed that
the walls should vibrate with the air.  I don't want to fully retract
that because vibration of the walls (especially walls made of
visco-elastic materials) are important, but I should point out that
you can describe musical instruments pretty well if you assume that
the walls of the instrument don't vibrate at all.  In that case, the
walls merely act as perfect reflectors of the sound waves.  In terms
of the interference patterns I described before, the sound waves must
merely interfere with their own echos within the waveguide, so to a
first order approximation the material isn't that important.  On the
other hand, for our _Parasaurolophus_ I should add that the soft
tissues will also absorb some of the sound energy, and this too will
effect the patterns (and hence the sounds) that could be created by
the living animal's head.

Am I making sense to anyone?

-- 
Mickey Rowe     (rowe@lepomis.psych.upenn.edu)